Semi-hollow rubber heel



Sept. 13, 1955 I J. A. PINAUD SEMI-HOLLOW RUBBER HEEL 2 Sheets-Sheet 1 Filed Feb. 12, 1952 Sept. 13, 1955 J. A. PINAUD 2,717,461

SEMI-HOLLOW RUBBER HEEL Filed Feb. 12, 1952 2 Sheets-Sheet 2 I N VEN TOR. l W A. p/flaud United States Patent O SEMI-HOLLOW RUBBER HEEL John A. Pinaud, Tampa, Fla.; Helen Burbank, administratrix of said John A. Pinaud, deceased, assignor to Pinaud Foot Research, Tampa, Fla., a corporation of Florida Application February 12, 1952, Serial N 0. 271,151

9 Claims. (Cl. 36-35) This invention relates to an improved rubber heel for shoes, and sets forth certain improvements over Pinaud Patents 1,977,695, dated October 23, 1934, and 2,198,228, dated April 23, 1940.

One of the main features in this novel rubber heel is to provide an improved structure that imparts to the foot of the wearer a support approximating that of level ground to a bare foot. This feature of improved construction of a rubber heel allows the use of shoes in such a manner that the walking by the wearer with shoes with these improved heels and improved shoe construction is substantially equivalent to the conditions of walking in primitive times before shoes with heels were provided.

Another feature is the provision of a hollow portion of the improved heel to allow collapsing of the hollow portion in an improved manner when the heel first engages the ground.

With the present day heels and the present day shoes, people are having very considerable foot trouble and many people are even required to use arch supports, which are for the purpose of trying to have the arches of the feet of the wearer especially supported in an effort to prevent pronation, or what is known as and usually called flat foot. With the improved construction of heel and shoe herein, this pronation is practically all eliminated by eliminating the cause therefor.

A further feature of the invention is to provide an improved rubber heel that embodies a portion which immediately collapses in a novel manner on the initial landing of the heel on the ground, and which then provides a definite support to the heel a short interval before the ball of the foot touches the ground. This definite actual support is located immediately under and in substantial vertical line with the supporting point of the heel bone of the foot. This improved heel conforms to the weight sustaining principle of the unclad foot in that it does not tend to overload the arch or as the conventional heel does.

Also a further feature of the improved heel described herein is that of providing a sloping rubber heel to give different thicknesses throughout its length so that when a a person stands full footed there is no compression of the plantar arteries of the foot. Whenever there is compression of these arteries, there is a reduction of the flow of blood through the foot and very often manifests itself by a tingling sensation in the sole of the foot thereby indicating a very serious impedance of proper blood flow.

A further feature and advantage of the improved invention reside in providing proper strength structure of the rubber heel at the surrounding portions of its collapsible part.

Another feature of this invention isthe provision of an improved rubber heel with a collapsible portion thereof in which the rear wall of the heel is constructed preferably to have a definite part thereof considerably more flexible than a second part of said wall and to have this rear wall preferably joined integrally with the floor of the collapsible portion of the heel to substantially form Patented Sept. 13, 1955 ice therewith a unit that bends only slightly within itself but which bends or swings as a unit during collapsing, thereby forcing the flexible part of the wall to fold in a manner so that no part of it engages the ground and becomes .worn. With this improved structure it has been noted that there is practically no sound emitted as the parts of the collapsible portion of the heel move to their normal collapsed positions.

Another feature of the invention is the improved construction of the floor of the collapsible portion of the heel so that, preferably, it is stiff enough by reason ofits thickness or by reason of reinforcement, to bend or swing about a natural or provided line during collapsing. This line of bending may be present by reason of a groove or scoring formed in the floor of the heel, or by having a part of the floor more flexible than the thick or reinforced part of the heel.

Other features and advantages of the invention will be apparent on the reading of the description, wherein Fig. 1 is a sectional view of the improved heel showing a collapsible portion and a muflle chamber, the section being taken on line 11 of Fig. 2;

Fig. 2 is a top plan view of the improved heel showing the collapsible portion and the muflle chamber;

Fig. 3 is a view partly in section taken partly along the right hand end of line 11 of Fig. 2, without showing the muflie chamber, but showing a part of the heel in collapse in a manner to create an infold of the rear wall and prevent the infold touching the ground, and showing the rear wall of the heel of varied thicknesses, and showing the rear part of the floor of the heel as substantially thicker than the thin portion of the rear wall;

Fig. 4 illustrates a heel in the same position as the heel in Fig. 3, but showing the rear or back wall of thin thickness throughout, and collapsing outwardly, and coming into engagement with the ground;

Fig. 5 is a modified view of a varied thickness of the floor of the collapsible part of said heel; i

Fig. 6 is also a modified view of the floor showing a relatively thick part and a groove or channel to allow flexing along a predetermined line;

Fig. 7 is a view somewhat similar to Figs. 5 and 6 with a stepped form of thickness of the floor of the collapsible portion of the heel and showing a groove for ready bend- Fig. 8 is also a modified view of the collapsible portion of said heel showing a reinforcement; A

Fig. 9 is a sectional view taken on line 1010 of Fig. 2 showing a relatively thick floor of the heel of substantially uniform thickness and being provided with a groove for guiding the flexing of the collapsible portion of the heel; Fig. 10 is like that of Fig. 9 except that the floor of the heel is of different thicknesses;

Fig. 11 shows a shoe partly in section and incorporating the improved heel of gradual thickness, and incorporating an improved shoe structure to provide a gradual straight sloping of the sole of the shoe from the region of the heel contact and extending to the ball of the foot, and showing a skeletonized bony and arterial structure of the foot in the shoe;

Fig. 12 is a sectional view on the line 12-12 of Fig. 11, showing the plantar arteries in their normal positions and not compressed;

Fig. 13 is a sectional, view somewhat like Fig. 12 except that it shows the plantar arteries out of their normal positions and compressed against the. bony structure as found inthe normal shoe of todays structure;

Fig. 14 illustrates, partly in section, a natural bony and arterial structure of an unclad foot in engagement with the ground; and

Fig. 15 is a bottom view of the left foot showing the bony and arterial structure. 4 i 1' Referring now to these drawings, the preferred structure of the improved heel is illustrated in Figs. 1 and 2.

The desired structure of the heel 27 embodies a rim 28 for engagement with the sole of the shoe, and a supporting part 29, and a collapsible portion 39, and a muffle chamber 31 connected to the collapsible portion by channels 32 and 33. An exit channel 34 is shown leading to the front of the heel. The front edge of the heel is represented at 36 and preferably is lower in height than the rear wall 37 of the collapsible portion 3t). By providing the muflie chamber 31 and the channels 32, 33 and 34, the heel functions quietly and in a most eflicient manner.

The Pinaud Patents 1,977,695 and 2,198,228 show a rubber heel with a hollow collapsible portion and a supporting part 29. The structures illustrated herein are improvements on those heels and provide for an improved desired type of heel that is long wearing, is not noisy, and during collapsing of the hollow portion will fold in a manner that prevents the rear wall from contacting with the ground and thereby prevents any material wear. In addition, the structure of the collapsible portion of the heel is such that there is little wear of the floor of the collapsible portion 30, and that the actual supporting part of the heel is positioned in relation to the collapsible portion so that at least the rear wall of the supporting part 29 of the heel comes under the actual bearing point of the heel bone of the foot, i. e., under the tubercles of the os calcis.

It is desired that the improved structure of the rubber heel at its hollow collapsible portion, has, in general, a relatively thick floor for joining with the rear wall. It is also desired that the lower part of the rear wall shall be of relatively stiff structure in relation to a thin or flexible structure of the upper part of the rear wall. Preferably the lower part of the rear wall is of varying thickness and will join the floor in any suitable manner, usually by integrally joining the floor and the lower part of the rear wall. In collapsing, the main area of the floor, usually the rear thereof, and the lower portion of the rear wall will practically swing as a unit, and the bending of the rear Wall will take place within the upper part thereof below rim 28. The swinging will take place along a line or any part of the floor which is provided with a more flexible structure than the rear or main area .of the floor. If desired, a groove or scoring may be formed in the floor thus to provide a definite line ,or curvature about which a definite flexing will take place.

In the drawing the preferred structure, Fig. 1, shows a floor 38 integral with the lower part 39 of the rear wall 37 and shows the more flexible part 4.0 of the rear wall 37 as being thinner and more flexible. The lower part 39 of the rear wall is illustrated as preferably being of varied thickness and joining the floor 38. A groove 41 is illustrated as providing a line about which the floor and rear wall 39 flex or swing as a unit and the thinner or more flexible portion 40 of the rear wall bends or flexes as shown in Fig. 3, and as so bent does not touch the ground. The foregoing description may be summarized by stating that the floor of the collapsible part of the heel is composed of different degrees of flexibility, and the rear wall construction is preferably of varying thicknesses usually having the thickened part extend upwardly approximately one-fourth the overall height so as to be capable of causing the infolding of the rear wall, as shown in Fig. 3.

While groove 41 provides a definite line of flexing, it will be understood that instead of the groove, the forward parts 42 and 43 of the floor may be made of more flexible rubber structure than the part of the floor to the rear of groove 41, and thus the rear area of the floor 38 may readily flex .or hinge around or about the more flexible portions 42 and 43 during the collapsing. While the groove 41 is shown as being at an angle to the longitudinal axis of the heel, it will he understood that such a groove may be formed or positioned at right angles to the longi in normal fashion.

tudinal axis of the heel. Also, the groove may be deep or may be of a shallow depth such as a scoring and be positioned as desired, i. e., at any angle to the longitudinal axis of the heel, or in any position in the inner surface of the floor, or may even be formed in the outside surface of the floor 38. Thus, by thiseasy swinging or bending, there will be the least wear of the heel, especially at its rear outer and lower edge.

While the floor 38 of the collapsible portion of the heel has been shown in Fig. l as relatively thick to accomplish the function of having the rear area of the floor swing as a unit preferably with the lower part of the rear Wall, an equivalent of this thickness is attained by providing suitable reinforcing ridges 44 and 45, as noted in Fig. 2. Any other suitable means for attaining this end may be provided.

It is to be noted that the upper part 40 of the rear wall 37 is preferably of uniform thickness. It will be understood that this part may be modified as desired so as to accomplish an in-folding of this part 40 when the hollow portion of the heel collapses. One form of accomplishing this in-folding result is by providing an added thickness such as horizontal band 47, as noted in Fig. 7, located approximately midway of the thin portion and encircling the surrounding back wall, and which may consist of a narrow band of thickened rubber or be reinforced by a flexible cord incorporated in the rubber, for the purpose of preventing the central part of the foldable portion of the back Wall from stretching during collapse of the rear cavity. In order that the middle portion of the thin part of the wall may protrude during collapse it must necessarily become elongated, which elongation or stretching is effectively prevented or restricted by the said reinforcing band, and in-folding is compelled. However, any other suitable means or structure may be incorporated to force such as in-folding. In most instances it is usual that the stiff or thickened part of the rear wall be approximately three times the thickness of the thin or more flexible part of the rear wall.

'With the preferred improved heel structure as already shown and described in Figs. 1 and 2, the collapsing of the collapsible portion 30 is illustrated in Fig. 3. The floor 38 is shown as engaging the ground Also, the floor shows the groove 41 as well closed, and shows the upper part 40 of the rear Wall flexed in an in-fold manner by bending at the top of the lower part 39 of the rear wall and at a point under the rim 28, the collapsing of the portion it) comes within the contour of the heel, and the top of the non-flexed portion of the rear wall will usually engage the bead 28. It will be noted that no part of the collapsible portion of the heel will engage the ground except the outside of the floor part which is specifically designed to contact the ground. The position of the heel as shown in Fig. 3 is that of the beginning of the heel engaging the ground and the hollow portion collapsed. As the person progresses in his step and the front part of the foot comes down on to the ground, then the heel takes the position as shown in Fig. 1.

For purposes of comparison, Fig. 4 illustrates an unacceptable form of collapsing parts of heels. The structure in Fig. 4 gives an out-fold due to the walls which allow the flexed part of the rear wall to engage the ground and thus become quickly worn.

Various modifications of the floor and the rear wall of the improved heel herein are illustrated in Figs. 5 to 10. These various structures illustrate manners in which the improved heels may be made to operate successfully. In Fig. 5 the floor 38 is shown as of increasing thickness as it extends from the supporting part 29 to the rear wall of the heel, and in this case the lower part of the rear wall is absorbed or incorporated in the back of the floor. In Fig. 6 the floor 38 is of substantially uniform thickness back of the rear-of groove 41.

In Fig. 7 the thickness of floor is less than shown in Figs. and 6, and the lower part 39 of rear wall 37 is shown of an increased thickness. In Fig. 8 the floor 38 is shown relatively thin and of uniform thickness but is provided with ridges of reinforcing elements 48 and the lower part of the rear wall 39 is shown with a suitable reinforcing ridge 49. Reinforcements 48 and 49 permit the floor 38 and the lower part of the rear wall 37 to swing as a unit during collapsing of this hollow part of the heel. These reinforcements are preferably reinforcing plates of comparatively rigid material and preferably are bonded to the rubber.

In Fig. 9 the structure of the heel shows a relatively thick floor 38 extending along to the muflie chamber 31. The floor is also shown as provided with a suitable groove 41 for purposes of guiding the bending. In Fig. 10 the floor 38 is shown of relative uniform thickness and the portion which extends forward and along the side of supporting part 29 is thinner, and is usually of uniform thickness. The juncture of the relatively thick and thin parts of the floor is noted in this figure.

In the study of construction and functioning of the human feet and of a covering therefor, now accepted in shoe form, there have been many experiments to provide a type of shoe structure that supports a foot in a manner which is comparable to the manner of natural and normal support before shoes of present design were available.

In the type of improved shoe design herein and from developments and actual experience, it has been found that the desirable shoe structure should have two particular features. The first one is to have a uniform slope of the shoe sole from the rear of the heel forward to the ball of the foot as will be noted in Fig. 11. The second feature is to have a heel for the improved shoe that has a hollow collapsible portion at the rear thereof, all as heretofore described; These features are illustrated in Fig. 11, where it will be noted that the improved heel 27 slopes from the rear wall 37 to its front wall 36, and the sole 51 of the shoe is noted as having the desired design slope.

Also, in the study of the human foot, for purposes of determining the proper support, especial consideration was had of the arteries of the feet, and it will be noted from Figs. 11 and 12 that the main artery 52 has branches or plantar arteries 53 and 54 which extend to the front of the foot, as shown in Figs. 11 and 12, and which are properly shown in their normal round cross-section form in Fig. 12, which figure is a sectional view of Fig. 11

or distortion of the arteries that supply the blood to the various parts of the foot. y

In showing the difference between the improved design of shoe and heel in Figs. 11 and 12 and the shoes as formerly designed and made,'reference is made to Fig. 13 wherein the foot is shown supported by shoes and heels of the present day type of design. In this Fig. 13 there is illustrated how the plantar arteries 53 and 54 are deformed by compressing them, and by forcing them up closely under the bones of the feet. These branch arteries, as shown compressed, prevent the normal flow of blood to the front of the foot.

Natures way of advising the wearer that the feet are not getting proper circulation and blood supply is by a tingling sensation known as the feet going to sleep. In providing this shoe structure with the sloping sole and an engaging heel having a sloping top to conform to the desired slope of the shoe sole, it is usually desired that the slope of the top of the heel along its longitudinal axis should be approximately inch in any 12 inches.

With the improved shoe heel herein having the hollow collapsible portion, it will be noted that the actual supporting part 29 of the heel is under the bones of the foot, and as noted above the arteries of the foot continue to supply the blood in proper and normal manner to the full area of the foot.

It is desired that the preferred improved heel herein shall be of any desired dimensions but shall have the proper supporting part and a collapsible portion. A heel of the preferred structure for a mans shoe may be noted as being approximately inch high at the rear wall and that its height at the front along the longitudinal center line shall be approximately inch high and that the height at the front side edges shall be approximately /2 inch high, and the overall length of the heel approximately three inches. With this collapsible structure of heel and where a grooveor scoring is employed on the top of the floor of the collapsible portion, it is preferable that the groove shall be approximately & inch in width at the bottom thereof and approximately inch in width at the top thereof. The depth of the groove may be suitable to provide for the efficient collapsing as described herein.

In referring to the drawings, it will be noted that the floor of the collapsible portion is desired to be thick and relatively stifi for at least the major part of its area so that it engages the ground without bending to any material extent and will flex about a more flexible part of the floor or about a provided groove or scoring. The stiffening of the floor is readily provided by a definite uniform thickness of rubber, or by a graduated thickness of rubber as noted in some of the figures of the drawings, or by stepped thicknesses, or by providing a reinforcement'in the form of ridges, orby stiffer material being attached to the floor as reinforcement or being incorporated in the floor. The rear wall of the collapsible portion of the heel usually has two or more different flexible parts or portions. Usually the lower part of the rear wall which joins the floor is less flexible than the upper part and this less flexible condition is obtained by making it of uniform or graduate thickness or by incorporating a reinforcing element. The upper part of this rear wall flexes materially. and allows the collapsing of the hollow portion and is provided in any definite thicknessaor structure as long as it is bendable and will not crack during long usage. It is also usual to have the lower part of the rear wall at least twice the thickness of the thinnest part of the rear wall. However, modifications may be made thereof so long as the thinner portion of the inner wall does not crack under usage.

With the cooperation of the floor of the collapsible portion of the heel and the lower part of the rear wall which preferably is integral with the floor, the collapsing of the hollow portion of the heel is accomplished without noise and in a manner that causes the least wearing of the heel. Also in this collapsing the thinner part of the rear wall has two particularly portions which bend materially, one of them being at the top of the thickened or stifi part of the rear wall, and the other at the point where the top of the rear wall joins the rim. Usually, the thickened or bottom part of the rear wall extends in height between A and of the height of the heel as measured from the bottom of the heel to the rim. When the height of the thickneed part of the rear wall is measured from inside the heel and above the top of the floor it may be said that the thickened part is usually approximately /s of the height of the rest of the distance between the top of the floor and the underside of the rim of the heel.

A representation of a bare foot with the bones thereof and the arteries therein, is shown in Figs. 14 and 15, wherein Fig. 15 is a view of the bottom'of a left foot. The artery 52 and the branch or plantar arteries 53 and 54 and the other arteries are illustrated in this bottom view of a foot. 1

When-the improved shoeand improved heel structures as noted in Figs. 11 and 12 areiemployed, thereis practically no pronation (fiat feet) developed by the wearer Also, these improved designs of shoe and heel prevent the inwardly canting of .the foot of .thewearer by eliminating the causes thereof.

From the foregoing descriptionit will benoted that the improved designsof the shoe soleand of the heel permit each foot to be properly supplied with blood nourishment, and by properly supporting the foot under the heel bone there will not be any overloading ofthe arch of the foot, and the plantar-or branch arteries will maintain their normal positions and not be subject to beingdisplaced -or compressed in a manner thatprevents proper flowofblood to all parts-of the foot. It will also be noted that the improved heel is quiet andhas long wearing qualities, and that with the semi-hollow-collapsible portion it gives a support to the foot that is equivalent to the normal bare foot when in engagement with the ground.

it will also be noted that with the improved-design of I the heel in forming the hollow collapsible portion that-it is helpful to provide a thick or reinforced floor of the collapsible portion and to have the lower part of the rear wall relatively thickor reinforced and as itis 'joinedwith the floor part, will usually swing with the door about a bending line or about a provided-groove-during collapsing. This improved part of the heel also provides for a rear wall to be of at least two-flexing abilities wherein the lower part flexes a little, but the upper part of the wall flexes easily and considerably sothat it-in-folds during the collapsing, thereby .preventing that part of the wall from engaging'the ground and being worn.

It will be understood that various modifications and changes may be made in thepreferred form ofthe invention herein, and such modifications andchanges are to be understood as part of this invention, as outlined in the following claims.

The invention claimed is: r

1. A semi-rubber heel having a hollowcollapsible portion at the rear thereof for allowing said-portion to collapse on initial impact of the rear edge of said heel'with the ground and having asupporting -portion of said heel in a semi-crescent shape and forming the forwardwallof said hollow portion, the remainder of said hollow portion being formed by a floor and a vertical outer wall joining said floor hear the outeredges thereof, said floor being considerably flexible adjacent the crescent shape of said supporting portion and being relatively thick throughout the remainder of the area of said floor to thereby allow the back part of said -fioor to swingas a unit more readily than a uniform thickness of floor throughout its full'area, said wall being of varied thicknesses to cause said wall to fold inwardly during thecollapsingof said hollow portion.

2. A semi-hollow collapsible rubber heel having 'a hollow portion at the rear thereof for allowing said portion to collapse on initial impact-of the rear edge of the heel with the ground and having a supporting portion of said heel forming the forward wall of said hollow portion, the remainder of said hollow portion being formed by a fioor and a vertical outer wall'joining said floor near the outer edges thereof, the rear portion of said floor being reinforced and having a scoring between said reinforcing part and the forward wall of said hollow portion to allow the reinforced portion of said heel to swing as a unit about said scoring, said wall being of graduated thicknesses to cause it to fold inwardly during collapsingof said hollow portion. I

3. A semi-hollow collapsible rubber heel having a hollow portion at the rear thereof for allowing-said portion to collapse on initial impact of the rear edge of the heel with the ground and having a supporting portion of said heel forming the forward wall of said hollow portion, the remainder of said hollow portion being formed by 'a floor and a vertical outer wall joining said fioornear the outer edges thereof, the rear portion of said floor being reinforced and having-a scoring between said reinforcing part and the forward wall of said hollow portion to allow the reinforced portion ofsaid heel to swing as a unit about said scoring, said scoring being formed at an angle to the longer .axis of said heel, said outer wall being of graduated thicknesses to cause it to fold inwardly during collapsing of said hollowportion. I

4. A rubber heel having a hollow collapsible portion near the rear thereof and a rim at its top edge and having afoot supporting part positioned forward of said collapsible portion and positioned to be under the os calcis bone of the foot, the collapsible portion of said heel having the fioor part thereof of uniform thickness and being approximately-twice the thickness of the thinnest part of the rear wall, said floor having a groove therein to allow flexing of said floor as a unit during collapsing, the rear wall-of said collapsible portion being tapered for at least one-fifth of its height from the top of said iioor to the thinnest part of said wall, and having the remainder of said vertical wall up to said rim of lesser thickness than said tapered part to provide for in-folding of said rear wall during the collapsing of said hemi-hollow portion.

5. A rubber heel having a hollow collapsible portion at the rear thereof and having a foot supporting part positioned forward of said collapsible portion and its rear edge positioned to be under the plantar tubercles of the os calcis bone of the foot, the collapsible portion of said heel having a thickened floor for engaging the ground and for allowing the floor to swing as unbendable unit, said floor having a groove to provide for said bending, said heel having -a back vertical wall of varying thickness providing for the collapsing of said hollow portion and for maintaining said back wall within said collapsible portion and preventing it from touching the ground.

'6. A rubber heel having a hollow collapsible portion at the rear thereof, and having a weight sustaining part forward of said collapsible portion, the rear edge of said sustaining part forming a front wall of said collapsible portion and being located under the plantar tubercles of the os calcis bone of the foot, said heel having a small area of the floor of said collapsible portion adjacent said front wall more flexible than the materially larger remaining area of said floor and having arear wall reinforced to at least one third of its overall height to require collapsing thereof only throughout the top part of its height. a

7. Arubber heel having a hollow collapsible portion at'the rear thereof, and having a weight sustaining part forward of said collapsible portion, the rear edge of said sustaining part forming a front Wall of said collapsible portion and being located under the plantar tubercles 'of the 0s calcis bone of the foot, said heel having a small area of the floor of said collapsible portion near the front thereof more flexible than the remaining part of the floor and having arear wall of-said collapsible portion of varying thicknesses with the thinness near the top of said heel.

8. A rubber heel having a hollow collapsible portion at the rear thereof, said hollow portion being collapsible on initial impact with the ground, said hollow portion having a front 311,11 fioor, and a rear wall, said front wall being positioned under the plantar tubercles of the os calcis bone of the foot, said floor having a flexible part adjacent said front wall'and having the remainder thereof stiffer than the part adjacent said front wall where by upon collapsing of said hollow portion the floor will flex about said more flexible part as an unbent unit, said rear wall being integral with the outer end of said floor and being of two thicknesses the greater of which joins the outer end of said "floor and the thinner joins the top of said heel, said rear wall upon the collapsing of said hollow portion having the thinner part thereof fold partially within the outline of said heel and at a positionthereof whereby this thinner portion will beout of contact with the ground. a

9. A rubber heel having a hollow collapsible portion at the rear thereof, said hollow portion having a front wall, a floor, and a rear wall, said front wall being positioned under the plantar tubercles of the os calcis bone of the foot, said front wall receiving the impact of the heel when originally hitting the ground, the floor of said heel adjacent said front wall being of less thickness than the remainder of said floor thereby providing a flexing portion of said floor to allow the remainder of said floor to flex as an unbent unit about said thinner portion, the end of said second portion of said floor being integral with said rear wall and extending up the height of said rear wall for not less than A inch from the lower outer edge of said heel and for not more than A inch from the top of said rear wall of said heel, said rear wall having a total height of approximately "V; inch and being unflexible at the bottom part thereof and being flexible References Cited in the file ofthis patent UNITED STATES PATENTS 2,033,399 Romano Mar. 10, 1936 2,198,228 Pinaud et al. Apr. 23, 1940 2,221,388 Sprovieri Nov. 12, 1940 2,394,281

Williams Feb. 5, 1946 

